December 29, 1923] 



NATURE 



927 



The Physiology of Sex-Determination. 



The Mechanism and Physiology of Sex Determination. 

 By Richard Goldschmidt. Translated by Prof. 

 William J. Dakin. Pp. ix + 259. (London : Methuen 

 and Co., Ltd., 1923.) 215. net. 



PROF. GOLDSCHMIDT gives us an object-lesson 

 in the way in which a single problem, at the 

 outset not apparently more important than a thousand 

 others, may, if pursued to its limit, be made to yield 

 results of the deepest importance and the widest 

 application. 



It has long been known to entomologists that crosses 

 between different species, and often also races, of Lepi- 

 doptera frequently produce a number of sexually 

 abnormal forms. This was the starting-point of the 

 investigation which has finally enabled Goldschmidt to 

 make his important contribution to the study of sex- 

 determination, and indeed to the problems of differentia- 

 tion in general. 



Put in the briefest possible way, we may sum up the 

 results of his twelve years of work upon the sexual 

 abnormalities arising in racial crosses of the Gipsy 

 moth {Lymantria dispar) as follows. In the first place, 

 since moths have two active sex-(X-)chromosomes in 

 the male, and one in the female, the male-determining 

 factors are in double dose in males, single dose in females. 

 The female-determining factor Goldschmidt has finally 

 located in the Y chromosome — an interesting fact, 

 since the work of the Morgan school on Drosophila has 

 shown that there the Y chromosome is without influence 

 upon sex-determination. He has next shown that the 

 strength or " potency " of the sex-determining factors 

 may vary, and does actually do so in the different sub- 

 species and races employed. It follows that when a 

 cross is made, the future distribution of the sex-factors 

 of various strengths, both male- and female-determin- 

 ing, can be prophesied from what we know of the 

 behaviour of the chromosomes, or, in other words, on 

 Neo-Mendclian principles. 



As to the mode of action of the female-determining 

 ^factor, we have the important fact that the Y must 

 exert its effect upon the growing oocyte, since we find 

 t the female-determining factor (which is inherited 

 purely maternally according to expectation) is effect- 

 ively present in males as well as females, although, of 

 course, in all eggs destined to give males the Y has been 

 eliminated in the polar body. If we are to draw con- 

 clusions, it appears that some substance, which Gold- 

 schmidt considers as of enzymatic nature, is given off 

 into the oocyte in quantity proportional to the 

 " potency " of the female-determining factor in the Y, 

 and exerts effects in embryonic development propor- 

 tional to its quantity. It is clear that if this is fully 



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substantiated, it gives us important clues as to the 

 possible mode of action of chromosomal genes. 



By these last facts we are introduced to the second 

 part of the problem — the mode of action of the sex- 

 factors during development in contradistinction to their 

 distribution to the gametes and zygotes — a field where 

 Goldschmidt has made his most signal contribution. 

 What do we start with ? — the presence in every male 

 moth of two doses of male-determining, and one dose 

 of female-determining substance; whereas in the female, 

 to the same quantity of female-determiner there is only 

 one dose of male-determiner. But, since normally, in 

 spite of the presence in individuals of either sex of 

 determiners for both sexes, we get only the two classes 

 male and female, we must say that (using the symbols 

 M and F for our two sex-determiners) 2M>F, whereas 

 F.-M. 



When different races were crossed, abnormalities 

 were produced. Goldschmidt was, in the first place, 

 able to demonstrate that, whatever the degree of 

 abnormality (and all degrees ?.re possible), they fell 

 into two classes, those which started their development 

 as females but ended it as males, and those which 

 started it as males and ended it as females. They 

 thus have no kinship with the other main type of sexual 

 abnormality known in insects, in which one half (or 

 some definite section) of the body is of one sex, the other 

 of the other. These latter animals are thus sex- 

 mosaics in space, whereas Goldschmidt's are sex- 

 mosaics in time. The term gynandrontorphs should be 

 restricted to the spatial type, the term intersex, or 

 better consecutive intersex, being used for the other. 

 The origin of gynandromorphs is to be sought in an 

 abnormality of mitosis whereby an X chromosome is 

 lost from one embryonic nucleus, whereas that of the 

 intersex is to be looked for in the faulty balance of 

 sex-factors. 



It is only in certain crosses that intersexuality 

 appears. An analysis of the families, together with the 

 above-mentioned discovery of the transformation of 

 sex during development in the intersexes, led to the 

 following far-reaching conclusions. Broadly speaking, 

 most of the Japanese races of the species possess sex- 

 factors of high potency, the European races of low 

 potency. Intersexes result (i) when a high-potency or 

 " strong " M (male-determiner) is combined with a 

 " weak " F — in which case the result is a female 

 intersex, or one which is genetically female and starts 

 its development as a female, but is later switched over 

 to maleness ; or (2) when two weak M's are combined 

 with a strong F, in which case male intersexes are 

 found. 



Further, within each main group, the separate races 

 may differ in regard to the strength of their sex-factors ; 



